75168-16-0Relevant articles and documents
Selective Activation of Reactant Molecules by Reversed Micelles
Yamagishi, Akihiko,Masui, Takeshi,Watanabe, Fumiyuki
, p. 281 - 285 (2007/10/02)
The oxidations by Ce(IV) ion of the cations of acridine orange (AOH+) and its N-alkyl derivatives (AO+-(CH2)nH) have been studied in water and in the reversed micellar system of cetylpyridinium chloride (CyPCl)/water/chloroform.The length of a substituting alkyl chain (n) is varied from methyl to octadecyl groups.In both media, the oxidation is found to proceed via the two-step mechanism: (1) AO+-(CH2)nH + Ce(IV) -> I + Ce(III) (k1) and (2) I + Ce(IV) -> P + Ce(III) (k2), where I and P denote the one- and two-electron oxidized species, respectively.In water, the bimolecular rate constants, k1 and k2, do not vary very much with the change of n; k1 = 7.0 X 104-14 X 104 M-1 s-1 and k2 = 2.1 X 104-5.9 X 104 M-1 s-1 for n = 0-9 at = 6.0 X 10-3 M, respectively.On the other hand, in the reversed micellar system, the first-order rate constant of step 1, k1, has a sharp maximum at n = 1; k1 = 1.9 s-1 (n = 0) -1 (n = 1) > 18-3.8 s-1 (n = 2-18). In contrast to this, the first-order rate constant of step 2, k2, is little dependent on n; k2 = 0.21-0.58 s-1 for n = 0-18 at = 8.8 X 10-3 M and = 5.6 X 10-2 M.The remarkably high rate of the initial step for AO+-CH3 is rationalized in terms of its favorable orientation at the boundary between the micellar water phase and the surfactant layer.
